teenager who took a terrifying plunge down an Alaska mountainside, all on the phone with her mom. She held on for life. Her mom called for help. ABC's Clayton Sandell has the story. Reporter: Take a look at this video. 18-year-old share Lareau, bringing to a cliff 90 feet in the air. Waiting for rescue, after falling 30 feet down a rocky mountain ridge. She set out Tuesday afternoon for what she thought would be a short hike to a waterfall, on denali national park. But not long into her walk, she took a frightening turn. Everything started getting slippery. Reporter: She reached out for help. I do when things get sketchy. I called my mom. Reporter: Her mom, 1,500 miles away in Washington state, answers the call. She is listening as the terrifying ordeal unfolds over the phone. I hear this scream. And sudden hysteria. It was all surreal. Reporter: Cherelle tried to keep calm. But the slightest movement could have sent her sliding down. She kept telling me, my feet are slipping. I had to say good-bye to my parents. It was awful. Reporter: Shelly stayed on the phone with Cherelle the entire time. They alerted Alaska state troopers. The rescue taking 45 minutes, captured by national geographic channel's Alaska state troopers. Thank you. Big hug. Reporter: This morning, she is safe. And so thankful. There's no doubt in my mind, I would not be here right now, if I would not have been on the phone with my mom at that time. Reporter: For "Good morning America," Clayton Sandell, ABC news, Denver.

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